You need to rent or purchase a good hammer drill.

Go a step further and get a rotohammer. I bought a good Makita the other
day for $25 at a yard sale. It has a SDS bit system, and has both the demo
hammer and rotohammer mode.

A hammer drill will get it done. A rotohammer will get it done in less than
half the time. They can be had at pawn shops, in the local Quick Quarter
rags, and at yard sales for prices that make it so that if you don't use it
much, you don't lose a lot of money.

The other day, we were ripping out caliche from where we want to put a
walkway. I needed a trench about three feet long and a foot deep and wide
for a French drain. I got out the Makita, and was done in a couple of
hours.

Get the rotohammer. You'll be glad you did.

Steve